Hello,
My configuration: VirtualBox (Windows10)
A simple question:
I listen to music on the Volumio server (VirtualBox), on the LAN (http: // volumio) and on the mobile phone (http: // volumio) but it’s the same music, where is the multiroom 
I am a beginner for 30 minutes 
“Multiroom” refers to accessing different Volumio devices from a single interface. So, if I have a device in the kitchen and one in the lounge, I can control either from the same browser address. In each case, the music that is played locally will be what that particular Volumio device is playing. Synchronised play of the same music source in different rooms can be achieved with the snapcast plugin.
Edit: your title is very misleading if you want advice from people. Sure include the info in the post (that’s good), but the post title should reflect your question/problem 
Thank you chsims1 for your help.